BS EN ISO 15927-3-2009 Hygrothermal performance of buildings - Calculation and presentation of climatic data - Calculation of a driving rain index for vertical surfaces from hourly.pdf

1、BS EN ISO 15927-3:2009ICS 07.060, 91.120.10NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDHygrothermal performance of buildings Calculation and presentation of climatic dataPart 3: Calculation of a driving rain index for vertical surfaces from hourly wind and r

2、ain dataThis British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 November 2009 BSI 2009ISBN 978 0 580 56101 6Amendments/corrigenda issued since publicationDate CommentsBS EN ISO 15927-3:2009National forewordThis British Standard is the UK implement

3、ation of EN ISO 15927-3:2009.The UK participation in its preparation was entrusted to Technical Committee B/540/8, Mirror committee for ISO/TC 163.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the ne

4、cessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 15927-3March 2009ICS 91.120.10; 07.060English VersionHygrothermal performance of

5、buildings - Calculation andpresentation of climatic data - Part 3: Calculation of a drivingrain index for vertical surfaces from hourly wind and rain data(ISO 15927-3:2009)Performance hygrothermique des btiments - Calcul etprsentation des donnes climatiques - Partie 3: Calculdun indice de pluie batt

6、ante pour surfaces verticales partir de donnes horaires de vent et de pluie (ISO 15927-3:2009)Wrme- und feuchteschutztechnisches Verhalten vonGebuden - Berechnung und Darstellung von Klimadaten -Teil 3: Berechnung des Schlagregenindexes fr senkrechteOberflchen aus stndlichen Wind- und Regendaten (IS

7、O15927-3:2009)This European Standard was approved by CEN on 31 January 2009.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliog

8、raphical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a

9、CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, It

10、aly, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: Avenue Marnix 17, B-1000 Br

11、ussels 2009 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 15927-3:2009: EBS EN ISO 15927-3:2009ISO 15927-3:2009(E) ISO 2009 All rights reserved vIntroduction This part of ISO 15927 specifies two procedures for analysing data de

12、rived from hourly observations of wind and rainfall so as to provide an estimate in terms of both an annual average and short-term spells of the quantity of water likely to impact on a wall of any given orientation. The first method, which uses hourly observations of wind and rainfall, is based clos

13、ely on BS 81041, which originated from a long series of measurements of driving rain on buildings in a wide range of locations within the UK. As such, the method applies to climates similar to those in the UK; in other regions, with very different climates, it is recommended that confirmation of its

14、 applicability be obtained by measurements of driving rain on representative buildings. Where hourly observations of wind and rain are not available, the second procedure, based on the present weather code for rain and average wind speeds can be used. In all cases, especially in mountainous areas, i

15、t is important that direct measurements of the rain impacting on building faades be made wherever possible. Rain penetration around the edges of doors and windows or similar cracks in building faades depends on shorter periods of heavy rain and strong winds. BS EN ISO 15927-3:2009BS EN ISO 15927-3:2

16、009INTERNATIONAL STANDARD ISO 15927-3:2009(E) ISO 2009 All rights reserved 1Hygrothermal performance of buildings Calculation and presentation of climatic data Part 3: Calculation of a driving rain index for vertical surfaces from hourly wind and rain data 1 Scope This part of ISO 15927 specifies tw

17、o procedures for providing an estimate of the quantity of water likely to impact on a wall of any given orientation. It takes account of topography, local sheltering and the type of building and wall. The first method, given in Clause 3 and based on coincident hourly rainfall and wind data, defines

18、a means of calculating the annual average index, which influences the moisture content of an absorbent surface, such as masonry, and the spell index, which influences the likelihood of rain penetration through masonry and joints in other walling systems. The second method, given in Clause 4 and base

19、d on average wind data and a qualitative recording of the presence and intensity of rain (the present weather code for rain), defines a means of calculating the spell length during which an absorbent material such as masonry is moistened, which has a 10 % probability of being exceeded in any year (c

20、ommonly referred to as having a mean return period of 10 years). A comparison between the two methods is given in informative Annex D. Procedures are given to correct the results of both methods for topography, local sheltering and the type of building and wall. The methods included in this part of

21、ISO 15927 do not apply in a) mountainous areas with sheer cliffs or deep gorges, b) areas in which more than 25 % of the annual rainfall comes from severe convective storms, c) areas and periods when a significant proportion of precipitation is made up of snow or hail. BS EN ISO 15927-3:2009ISO 1592

22、7-3:2009(E) 2 ISO 2009 All rights reserved2 Terms, definitions, symbols and units For the purposes of this document, the following terms, definitions, symbols and units apply. 2.1 Definitions 2.1.1 spell period, or sequence of periods, of wind-driven rain on a vertical surface of given orientation N

23、OTE Further information about spells is given in Annex B. 2.1.2 airfield hourly index quantity of driving rain that would occur on a vertical wall of given orientation per square metre of wall during 1 h at a height of 10 m above ground level in the middle of an airfield, at the geographical locatio

24、n of the wall 2.1.3 airfield annual index airfield index for a given wall orientation totalled over one year 2.1.4 airfield spell index airfield index for a given wall orientation totalled over the worst spell likely to occur in any three-year period 2.1.5 wall annual index quantity of wind-driven r

25、ain per square metre at a point on a wall of given orientation, based on the airfield annual index and corrections for roughness, topography, obstruction and wall factors 2.1.6 wall spell index quantity of wind-driven rain per square metre at a point on a given wall, based on the airfield spell inde

26、x and corrections for roughness, topography, obstruction and wall factors 2.1.7 line of sight horizontal view away from the wall, over a sector spanning about 25 either side of the normal to the wall 2.1.8 terrain roughness category classification of the surface roughness upwind in terms of the aver

27、age height and spacing of obstructions such as buildings, trees or hedges 2.1.9 roughness coefficient factor that allows for the modification of the wind speed by the roughness of the terrain upwind of a wall 2.1.10 topography coefficient factor that allows for the effect of local topography on the

28、wind speed 2.1.11 obstruction factor factor that relates to shelter from the very local environment and allows for obstructions such as buildings, fences and trees close to, and upwind of, the wall 2.1.12 wall factor ratio of the quantity of water hitting a wall to the quantity passing through an eq

29、uivalent unobstructed space, allowing for the characteristics of the wall BS EN ISO 15927-3:2009ISO 15927-3:2009(E) ISO 2009 All rights reserved 32.1.13 wall orientation angle between north and line normal to a wall 2.1.14 convective storm heavy precipitation in the form of showers or thunderstorms

30、generally lasting less than 1 h 2.1.15 reference spell period during which a wall oriented in any given direction is moistened, having a 10 % probability of being exceeded in any year 2.1.16 present weather code numerical code used by meteorological observers to assess the weather conditions at the

31、time of an observation NOTE Present weather codes are given in the WMO Guide2. 2.1.17 half day twelve-hour period including the hours from 07:00 to 18:00 or from 19:00 to 06:00 2.2 Symbols and units Symbol Quantity Unit CRroughness coefficient CTtopography coefficient D hourly mean wind direction fr

32、om north H effective height of feature m IAairfield annual index l/m2ISairfield spell index l/m2IWAwall annual index l/m2IWSwall spell index l/m2KRterrain factor L length m N number of years of available data O obstruction factor r hourly rainfall total mm v hourly mean wind speed m/s W wall factor

33、x horizontal distance m z height above ground m z0roughness length m zminminimum height m wall orientation relative to north BS EN ISO 15927-3:2009ISO 15927-3:2009(E) 4 ISO 2009 All rights reserved3 Calculation of airfield indices from hourly wind and rain data 3.1 Sources of data Data used for calc

34、ulations according to this part of ISO 15927 shall have been measured by the methods specified by the World Meteorological Organization (see WMO Guide2). 3.2 Airfield annual index For any location with at least 10 (and preferably 20 or 30) years of hourly values of wind speed, wind direction and rai

35、nfall, the annual index for wall orientation, , is given by Equation (1). vr D IN=89Acos( )29(1) where the summation is taken over all hours for which cos(D ) is positive, i.e. all those occasions when the wind is blowing against the wall. As the wind speed during rainfall is not generally the same

36、as in dry weather, calculating the product of hourly averages of wind and rainfall is not strictly accurate, especially in showery weather. It has been shown, however, that the error is small and, in any case, several years of data for periods shorter than 1 h are available from very few places. Tak

37、ing the product of the averages over days or months does lead to serious inaccuracies and should not be used for calculating driving rain indices. 3.3 Airfield spell index For any location with at least 10 (and preferably 20 or 30) years of hourly values of wind speed, wind direction and rainfall, f

38、or each wall orientation, , and for each spell of driving rain (see Annex B), calculate SI using Equation (2). ()IvrD =89S2cos9(2) where the summation is taken over all hours in the spell for which cos(D ) is positive, i.e. all those occasions when the wind is blowing against the wall. The 67 %perce

39、ntile (i.e. the value for which 33 % of the SI values are higher) is found from the values of SI for all the spells within the period of available data. The 67 % percentile defines the spell index, IS(i.e. the maximum value of SI likely to occur once every three years). 4 Estimation of the effect of

40、 driving rain from average wind and present weather code for rain The available data are divided into twelve-hour periods (07:00 18:00 and 19:00 06:00) called half days. A half day is defined as “moistening” if all of the following conditions apply. a) There is more than 4 mm of precipitation on a h

41、orizontal surface in the half day. b) The present weather code reports some precipitation for at least three of the five three-hourly observations during the half day (i.e. at 06:00, 09:00, 12:00, 15:00 and 18:00 and at 18:00, 21:00, 00:00, 03:00 and 06:00). NOTE Present weather codes of 50 or above

42、 indicate some form of precipitation. BS EN ISO 15927-3:2009ISO 15927-3:2009(E) ISO 2009 All rights reserved 5c) The average wind speed during the half day is greater than 2 m/s. d) The average wind direction during the half day is within 60 of the perpendicular to the wall, i.e. 60D u . Under these

43、 conditions, it is assumed that a wall surface will be wetted by driving rain, with subsequent water migration into the wall by capillarity. A half day is defined as “drying” if all of the following conditions apply. The average atmospheric relative humidity during the half day is less than 70 %. Th

44、e average wind speed during the half day is greater than 2 m/s. The average wind direction during the half day is within 60 of the perpendicular to the wall, i.e. 60D u . Under these conditions, it is assumed that the wind and atmospheric humidity allow the evaporation of water at the wall surface.

45、All other atmospheric conditions are considered neutral. A moistening half day is given the value “+1”, a drying half day “1” and a neutral half day “0”. The successive values are added to give a cumulative time series, with the constraint that the total does not fall below zero; a maximum value, eq

46、ual to the length in half days of the longest moistening spell in the year, is deduced for each year and each wall orientation. The cumulative distribution of annual maximum, established from NYyears of meteorological data, is then fitted by a Gumbel function1). This is used to obtain the reference

47、spell, which is the maximum spell occurring once every 10 years for a given meteorological station and a given wall orientation. 5 Calculation of wall indices 5.1 General The airfield indices calculated in Clause 3 are the amounts that would be collected by a free-standing driving-rain gauge in flat

48、 open country. They are converted into wall indices (i.e. the amounts of rain that would impact on a real wall) by multiplying by the terrain roughness coefficient, CR, the topography coefficient, CT, the obstruction factor, O, and the wall factor, W, as given in Equations (3) and (4). I ICCOW=WA A

49、R T(3) I ICCOW=WS S R T(4) These corrections can also be applied to the reference spell derived from the method defined in Clause 4. 1) The cumulative distribution of annual maximum is fitted by the Gumbel function () exp expX aFXb =where a is the mode and b the dispersion parameter. F(X) is the probability of X not being exceeded during one year. BS EN ISO 15927-3:2009ISO 15927-3:2009(E) 6 ISO 2009 All rights reserved5.2 Roughness coefficient The roughnes